Officials are probing how a 51-year-old highway bridge came to collapse in the Italian port city of Genoa yesterday, killing at least 26 people and injuring 16 others as it sent dozens of vehicles tumbling into a heap of concrete and twisted steel.

Federal GST pledge as WA by-election looms

The federal government's new self-imposed deadline to improve the GST carve up is politically motivated with the Perth by-election looming, WA Treasurer Ben Wyatt says.

Federal Treasurer Scott Morrison says he is seeking to fix weakness in the distribution "well before" the next federal election, conceding the government needs to do more than offer "band aid" cash for infrastructure projects.

"I suspect the interest in WA's unfair GST is only because we are in a political sweet spot and I think that has emerged with the by-election coming up in Perth," Mr Wyatt told reporters on Monday.

The by-election has been triggered by the sudden resignation last week of Labor's Member for Perth Tim Hammond.

The federal government recently committed $3.2 billion for WA infrastructure projects, but the cash will be spread out over several years compared to two years for Labor's previously announced $1.6 billion infrastructure fund.

Chamber of Commerce and Industry WA chief economist Rick Newnham said short-term top-ups could no longer be the answer.

"Structural change must be made to encourage all states to grow their own economy," Mr Newham said.